1. Field of the Invention
The present invention provides an improvement to a chemical canister. In particular, a rigid bracket is provided that clamps to a sturdy element of the canister. Valves and other articles associated with the canister may be attached to the bracket for support and protection.
2. Background
Industrial chemicals are often shipped and stored in small canisters, for example, 2, 5 or 10 gallon canisters, such as so-called "1A1 " containers. In many instances, these canisters must be absolutely air-tight and leak-proof, either because the chemicals present health or environmental hazards or other dangers, or because the chemicals will become contaminated and unusable after even a slight exposure to air or other substances. Means are therefore provided in the art for filling, connecting, and using such canisters without exposing the chemicals contained therein to the environment.
Referring to FIG. 1, the top of a typical chemical canister is shown, as will be familiar to those having skill in the art. Canister top cap 12 is typically welded to canister body 14 to form an enclosed, sealed container. Top cap 12 may be provided with a port tube 16 which penetrates and is welded to top cap 12 (see FIG. 6). Port tube 16 cannot be seen in FIG. 1 because it is obscured by port tube nut 18, which sealably closes the external end of port tube 16. The external end of port tube 16 is typically threaded to engage nut 18 or other apparatus (such as a level sensor) that may be coupled thereto. Port tube 16 may typically be about 2 inches in diameter. The canister, port tube and other components of the canister assembly may be made of metal, typically stainless steel.
Top cap 12 is also typically fitted with several delivery tubes 20, which provide connections to the interior of the canister for filling and using the canister. Inside of the canister, a delivery tube may extend to near the bottom of the canister, forming a dip tube used for extracting fluid from the canister, or it may extend only a short distance into the canister. In a typical application, a dip tube is used to conduct the contents out of the canister, while a gas source is applied to another delivery tube to pressurize the canister and thereby force the fluid contained in the canister out through the dip tube. The outside of each delivery tube 20 is sealably connected to top cap 12, such as by welding. The end of each tube external to the canister is formed into a sealing gland for use in connecting the tube to other apparatus. In common applications the sealing gland is a "VCR" gland. A captive threaded nut or collar 22 is provided around each delivery tube 20 between the canister and the gland.
FIG. 2 shows a cross sectional view of a typical VCR connection. As is well known in the art, this type of connection may be used to provide an ultra-pure seal but is subject to damage and leaking. Lower gland 24 is connected to tube 20. Upper gland 26 is connected to other apparatus to be attached to the canister, such as valve 28 (see FIG. 1). Each gland has a precisely machined sealing surface 30, 32 and a compression shoulder 34, 36. To form the VCR connection, a VCR washer 40 is positioned between sealing surfaces 30 and 32. Compression shoulder 34 is engaged by an internal shoulder on threaded collar 22 (see FIG. 1), and compression shoulder 36 is engaged by an internal shoulder on opposing collar 23. Collars 22, 23 and connector body 38 have corresponding threads, and as they are threaded together they apply opposing compression forces to shoulders 34 and 36, thus compressing VCR washer 40 between sealing surfaces 30 and 32, effecting the required ultra-pure coupling. A similar VCR connection may be provided between the top end of VCR body 38 and valve 28 or blank plug 42.
While this patent refers to embodiments employing VCR couplings, the present invention applies equally to embodiments employing other types or arrangements of connectors and couplings. The references to VCR couplings are therefore exemplary and not limiting of the scope of the invention, which is defined by the claims that are appended hereto. Furthermore, references in this description to particular dimensions and canister configurations are also exemplary and are not intended to limit the scope of the invention.
It will be appreciated by those skilled in the art that a VCR connection is fragile, and that if an unusual force is applied to such a connection it may be damaged and lose its seal. As can be seen in FIG. 1, additional VCR couplings 44 or other types of connectors may be provided on top of valves 28 in order to provide attachment points for process piping when the canisters are filled or used. When process piping (not shown) is connected to the top of valve 28, valve 28 should be firmly supported ("backed-up") to avoid applying torque or bending forces to the VCR seal that is formed between valve 28 and tubing 20. If such support is not provided, the seal may be damaged.
Canisters are typically shipped with valves 28 and actuators 46 attached. If a canister is dropped or if a valve 28 is bumped during shipment or handling, the VCR seals between valve 28 and canister top cap 12 are a likely place for damage to occur, resulting in leakage from the canister or spoilage of its contents. If the canister contains toxic or hazardous materials, the occurrence of a leak can result in substantial cost and inconvenience. It is therefore imperative that apparatus be provided for preventing leaks from occurring in these seals.
It is thus desirable to provide a canister/valve arrangement that is less vulnerable to damage and leaking during shipping and handling than is known in the prior art described above. It is also desirable to provide a canister that may be quickly and easily attached to process piping without excessive concern for supporting or backing-up the valves and couplings that are mounted on the canister. It is further desirable to achieve these objectives without having to modify or to compromise the integrity of existing chemical canisters.